The video clip shot by a Romanian TV channel showing Hungarian police officers pretending to stop migrants from entering the country. The symbolic presence of police officers in the border region and their lack of effective action to halt the flow of migrants into the country are part of spectacle.
Probably, the Hungarian government was warned that its decision to disrupt the flow of migrants into Europe makes certain forces unhappy. Most likely, the government was told in no ambiguous terms that its anti-migrant policy can only be symbolic otherwise, punitive measures will follow.

Probably, the migrants were coached by agents of influence telling them don't be afraid of confronting border guards or police officers because they can't harm you.